Phosporous removal from animal waste

ABSTRACT

The subject invention is related to a method for removing bio-available phosphorus from animal waste and soil using an industrial byproduct from a metal manufacturing process. The byproduct is used to treat organic waste, such as animal waste and poultry litter, and immobilize bio-available phosphorus present in them. The byproduct is also used to treat organic waste to produce fertilizers, which are used to amend the soil and control the level of phosphorous present in the soil. The disclosed method strikes a balance between providing enough nutrients to the soil to grow crops, while preventing loss of phosphorous to surface water.

This application is a 371 of PCT/US99/28615, filed Dec. 3, 1999.

This application claims priority to U.S. Provisional Patent ApplicationSer. No. 60/110,876, filed Dec. 4, 1998, the entire contents of whichare incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to a method of reducing phosphoruspollution from agricultural runoff. The present invention also relatesto a method of immobilizing bio-available phosphorus in organic wasteproducts using high phosphorus affinity material capable of forminginsoluble metal-phosphorus complexes. In addition, the presentapplication relates to a method of making fertilizer comprising adesignated amount of phosphorus

Although the evidence is circumstantial and inconclusive at this point,it has been suggested that nutrients lost from farm lands through runoffand leaching may be partially responsible for the outbreaks ofPfiesteria-like organisms in various rivers along the Atlantic coast.Nutrients enter water from many sources. Sewage sludge, septic tankeffluent, organic manufacturing waste, and animal manure contain highconcentrations of nitrogen and phosphorus.

Farmers commonly obtain nutrients for their crops from inorganiccommercial fertilizers and from organic sources such as animal manureand biosolids from wastewater treatment plants. Generally, inorganicnitrogen and phosphorus compounds are water soluble and readilyavailable to plants. In contrast, most organic nutrient sources containboth inorganic forms of nutrients and forms that must first bemineralized or decomposed to become available to plants. The movement ofnitrogen and phosphorus through soil are different. If nitrogen isconverted to the highly water soluble nitrate-nitrogen form, and is notused during plant growth, it can move through the soil-water system andbe vulnerable to leaching into the groundwater. In the same way, soilsamended with large quantities of organic or inorganic phosphorus maygenerate significant amounts of soluble phosphorus that can be readilytransported by surface and subsurface runoff and groundwater leachate.

When organic sources of nutrients are used, the ratios of nitrogen andphosphorus do not usually correlate with the crop's actual nutrientneeds. The phosphorus to nitrogen ratio required by plants (1:6) isusually much smaller than the ratio found in manure (1:1-1:2). Hence,nitrogen-based application of manure to agricultural fields results inthe application of phosphorus in excess of plant nutrient requirements.

In animal waste, phosphorus occurs in both dissolved (soluble) andparticulate forms. Phosphorus losses from agricultural systems, otherthan by crop removal, generally occur through the following pathwaysassociated with surface water runoff: a) particulate losses either asphosphorus absorbed into soil particles or organic materials, and/or b)soluble inorganic and organic phosphorus compounds.

Various methods have been suggested to reduce soil erosion, which alsoreduces particulate phosphorus in runoff. These are, among others:no-till farming, contour/strip cropping, grass waterways, bufferedstreams, and related structural controls. While efforts to reducesediment in agricultural runoff often reduce particulate phosphorus,they do not reduce losses of dissolved phosphorus, thus increasing thepercentage of total phosphorus in runoff that is immediately availablefor biological uptake. Consequently, recent efforts on improving waterquality of surface waters has focused on reducing soluble, bioavailabledissolved phosphorus.

With commercial fertilizers, it is possible to tailor the ratios ofnitrogen and phosphorus to meet the crop's nutrient needs. In the past,organic nutrient sources were typically applied to the soil to meet thecrop nitrogen requirements, without regard for the phosphorus content inthe soil. Nitrogen-based plans have made use of animal wastes, been costeffective, and reduced nitrogen application to land. However, this hasresulted in overapplication of phosphorus. These applications frequentlyoccur on soils with that already have high phosphorus content caused byrepeated, long-term applications of organic fertilizers. Thisoverapplication increases the potential for phosphorus to move fromfarmland to nearby water.

One method to reduce soluble phosphorus in runoff and leachate is tobase application rates of organic fertilizer sources on the recommendedcrop phosphorus requirements. Phosphorus-based nutrient management planscan be applied to fields with a very high potential for phosphorus lossto surface water. However, using P-based application of organicfertilizers results in underapplication of nitrogen. In such asituation, additional nitrogen from other sources—most likely commercialnitrogen fertilizers—must be added to supplement the fertilizer. Thus,there is a necessity to develop a system that allows for the optimum useof organic sources of nutrients while maintaining environmentalintegrity.

In Maryland, soil test phosphorus values will be the critical factor indetermining whether animal manure can be applied according to cropnitrogen requirements. For soils that test in the “excessive phosphorus”range, nutrient managers are required to perform a Phosphorus Site Index(PSI) assessment (The Maryland Phosphorus Site Index: A Technical User'sGuide (Version I). August 1999. Agricultural Nutrient Management Programand MD Cooperative Extension. Univ. of MD, College Park, Md., which isincorporated herein by reference in its entirety). The PSI takes intoconsideration factors such as soil test phosphorus, soil type,fertilizer source and phosphorus availability, slope, buffer strips,runoff potential and cropping methods to derive a final rating based onthe potential for phosphorus loss to surface waters. The final rating isbased on 5 categories (high risk to low risk) on which phosphorusapplication guidelines are based. A low risk rating will allow for thecontinued application of manure based on nitrogen requirements, while amedium to high risk rating indicates that phosphorus applications willeither be limited to annual crop requirements or eliminated completely.

While phosphorus based application rates of organic fertilizers would beenvironmentally sound and should begin to limit both phosphorus andnitrogen enrichment of the associated water bodies, this type ofplanning would have a very serious and potentially expensive impact onfarms that generate or use animal manure. Adopting phosphorus-basednutrient management plans would increase operation and crop productioncosts. Major changes to current farming practices would involveimporting of fertilizer nitrogen and exporting of manure. These types ofactivities can have a significant negative impact on the profitabilityof any farming system.

Among the significant contributors to the fertilizer industry are thepoultry growers. In the poultry industry, approximately 625 millionbirds (three billion pounds of meat) are raised each year on theDelmarva Peninsula Assuming these flocks are fed according to theNational Research Council recommendations, 53 million pounds of manurenitrogen and 22 million pounds of manure phosphorus are excreted peryear. Poultry farming therefore represent one of the significant sourcesof nutrients that have a potential impact on water resources.

Many of the lower Eastern Shore counties in Maryland have inadequatecropland available for efficient utilization of manure phosphorus,therefore, alternative disposal options have been suggested.Transporting nutrients to areas of the state or region where soils donot contain excessive concentrations of phosphorus and where phosphorusinputs are necessary for optimum crop production is one solution.However, distribution is not so much limited by lack of availabletechnology but rather by the economics of transporting manure longdistances.

Burning manure is another disposal option. In the early 1980's, DelmarvaPower burned broiler litter in their Indian River Generation Facility atMillsboro, Del. However, litter supply still remains a problem. The BTUvalue of broiler litter is about 6,800 BTU's per pound at 30 percentmoisture in a large fluid bed burner. The ash content for broiler litteris approximately 11.3 percent. This shows a large volume and weightreduction. Burning raw litter in small on-farm furnaces has presentedsome problems such as slag formation because of incomplete combustion,odors, particulate, and loading difficulties.

Regardless of any other measures either to reduce the phosphorus contentof manure or to find alternative uses for manure, these actions willhave no effect on soils that already have high phosphorus levels and areat risk for phosphorus losses to the surrounding environment throughsurface water. However, remediation of high-phosphorus soils has neverbeen implemented on a large scale. Hence, no standard practice exists.

Methods of removing excess phosphorus from the soil include using crops,and tillage methods. Since plants take up phosphorus, growing cropswithout adding phosphorus to the soil provides an income source (crops)and leaves the soil undisturbed. However, this process will require theapplication of nitrogen, which is an expense to the farmer, as well ashaving a pollution potential of its own.

A novel variation of mining phosphorus through crop removal, calledphytoremediation, is being explored for removing inorganic contaminantsfrom soil. Phytoremediation, or “Green Remediation” uses unusual plantsthat have developed the ability to concentrate high levels of elements,usually heavy metals, in plant tissue. The primary limitation ofphosphorus phytomining is no one has identified reliable phosphorushyperaccumulators.

Tillage, an immobilization technique, would place the phosphorus-richsurface soil well below the surface and out of reach of surface runoffwater, hence effectively stopping surface transport of phosphorus. Thephosphorus would be below the surface but still within the root zone,enabling it to be taken up by plants over time. One major concern isthat the soil that would be brought to the surface must be equally goodfor crop production, or else, it would create a permanent liability forthe farmer. Furthermore, the subsurface soils that are brought to thesurface must also be low in phosphorus or tillage will have no impact.The ramification of this is that extensive soil testing of the deepersoil would be necessary prior to performing tillage, and it would not besuitable on some farms.

Thus, there exists a need in the agriculture field for a more effectiveand cost-efficient method for immobilizing phosphorus without harmingthe environment.

Turning to an unrelated field, in the metal refining or manufacturingindustry, byproducts are considered environmental hazards. In thetitanium dioxide pigment manufacturing process, for example, there canbe mentioned two refining or manufacturing methods—sulfuric acid andchlorine. Both of these known industrial methods, however, involveenvironmental pollution, although the chlorine method pollutes somewhatless.

The sulfate method is a relatively low-technology, batch manufactureprocess, and is described in U.S. Pat. No. 4,186,088, which isincorporated herein by reference in its entirety. The sulfuric acidmethod is advantageous for refining titanium because the startingtitanium-containing material is not particularly limited, and an orehaving a titanium oxide content of 50 to 60% by weight, for instance,ilmenite, can be used as the starting material. But large quantities ofwastes are formed. More specifically, it is said that 3 to 4 tons ofiron oxide hydrate and about 8 tons of dilute sulfuric acid are formedfor 1 ton of titanium oxide produced. Environmental concerns prohibitdiscarding these wastes formed in such large quantities into rivers orseas. Further, if these wastes are treated again in a particulartreatment plant to recover valuable resources, the manufacturing cost isinevitably increased. It is said that the manufacturing cost isincreased by about 15% by this treatment of the wastes.

The chlorine method, on the other hand, is a relatively high technology,continuous process. If the chlorine method is adopted for the productionof titanium oxide, the problem of wastes is not so acute. The rawmaterial used in the method is typically a rutile ore having a titaniumoxide content of at least 90% by weight. A high purity rutile ore suchas mentioned above is reacted with chlorine gas to form titaniumtetrachloride, which is reacted with oxygen to form titanium oxide andchlorine. The byproducts of these industrial metal-refining processesare typically rich in iron.

The metals refined by the above processes are filtered, washed, anddried. The dried pigments are treated with organic solvents, ground, andpacked or slurried with appropriate dispersants.

The chlorine and sulfuric acid processes for making metal oxides, suchas TiO₂, are described in Braun et al., “TiO₂ pigment technology: areview,” Progress in Organic Coatings, 20, 105-138 (1992), and Braun,“Titanium Dioxide—A Review,” Journal of Coatings Technology, Vol. 69,No. 868, 59-72, (1997), which are incorporated herein by reference intheir entirety.

The discharges of the metal refining process, such as in the titaniumdioxide pigment manufacturing process discussed above, which includeiron compounds, dilute acids and miscellaneous inorganic contaminants ofthe ore, have become international environmental issues. The cost ofwaste disposal has been responsible for large increases in themanufacturing costs of the pigments made from titanium dioxide.Currently, these byproducts are disposed of in landfills. This is not asatisfactory solution to the waste disposal problem because landfillingthe byproduct does not benefit the environment and is costly to themanufacturing companies.

Offiah, O. and D. S. Fanning. 1994. Liming value determination of acalcareous, gypsiferous waste for acid sulfate soil. J. Environ. Qual.23:331-337 discloses adding lime to calcareous and gypsiferous soil toraise the pH of the soil. However, the reference does not discloseremoving phosphorus from the soil using the calcium and iron containingmixture such as an industrial byproduct of a metal refining ormanufacturing process of the invention.

Hughes, K. J. and L. R. Cooperband. 1998. SWAN-gypsum as a potentialsoil amendment for reducing phosphorus in a constructed wetlandreceiving milking parlor effluent. 1998 Annual meeting abstracts. ASA,CSSA and SSSA. Baltimore, Md. October 18-22, is directed to mixingSWAN-gypsum with a constructed wetland soil. However, the reference doesnot disclose using the inventive composition as a direct additive toagricultural soil, animal waste, or liquid waste to remove phosphorus.

Hsu, P. H. 1976. Comparison of iron (III) and aluminum in precipitationof phosphate from solutions. Water Research. 10:903-907, reported thatthe optimum phosphorus removal by Fe occurred in the pH range of(4.1-7.1), while optimum phosphorus removal by Al occurred in the pHrange of (5.5-8.0). However, the reference does not disclose using theinventive composition for treating agricultural soil, animal waste, orliquid waste to remove phosphorus.

Cooke, G. D. et al. 1986. Lake and reservoir restoration. Ann ArborScience Book, Boston, Mass. also demonstrated phosphorus removal bysorption on aluminum hydroxide surfaces in a pH range of 6 to 8. Even insolutions with low concentration of Ca²⁺, phosphorus removal can occurvia adsorption onto calcite surfaces. However, the reference does notdisclose using the inventive composition for treating agricultural soil,animal waste, or liquid waste to remove phosphorus.

Moore, Jr., P. A., and D. M. Miller. 1994. Decreasing phosphorussolubility in poultry litter with aluminum, calcium and iron amendments.J. Environ. Qual. 23: 325-330 is directed to methods for reducingsoluble phosphorus in poultry litter with aluminum, calcium and ironamendments. However, the reference does not disclose using the inventivecomposition for treating agricultural soil, animal waste, or liquidwaste to remove phosphorus.

EP 0 650 515 B1 discloses producing a binding agent made of gypsum,titanium hydroxide and iron hydroxide compounds that are used forstabilizing and strengthening soil or clay so that buildings can beconstructed on the modified soil. The reference is unconcerned withphosphorus removal.

Barksdale, Titanium, Its Occurrence, Chemistry, and Technology, secondedition, The Ronald Press Co., NY (1966), describes the chemistry oftitanium as well as the sources of titanium and its extraction andmanufacture. This reference is incorporated herein by reference in itsentirety.

Fitch et al. (U.S. Pat. No. 4,186,088) is directed to a process ofneutralizing the waste stream from a sulfuric acid-based extractionprocedure from titanium containing ores. A byproduct of the secondaryneutralization operation, in particular, has neutral pH and has lowconcentrations of metals, excluding iron which is present at levels inexcess of 10%. The patent does not discuss removing phosphorus fromanimal waste using the byproducts that are described. U.S. Pat. No.4,186,088 is incorporated herein by reference in its entirety for itsdescription of the process of neutralizing the waste stream obtainedthrough the titanium extraction process, thereby obtaining the byproductSecondary Waste Acid Neutralization, or SWAN, gypsum.

Thus, there remains a need in the farming, animal growing and nutrientmanagement industries for a method of removing or immobilizingbio-available phosphorus from animal waste such as poultry litter sothat such animal waste can continue to be applied to the field and usedas primary nitrogen source for crops, while minimizing loss ofphosphorus to surface water. There is also a need in the metal oxidemanufacturing industry, such as titanium dioxide, for an environmentallysafe and cost-effective method of disposing of industrial byproducts.

SUMMARY OF THE INVENTION

The present invention has met the hereinbefore-described need.

For the first time, a process has been developed that solves twoproblems in two different fields—overabundance of bio-availablephosphorus in certain soil and organic waste that leads to thephosphorus in runoff water, and waste disposal problem generated by themetal manufacturing process, such as titanium dioxide. The solutioninvolves using heretofore considered unusable byproducts of the metaloxide manufacturing process to immobilize bio-available phosphoruspresent in the soil and organic waste. The abundant quantity ofbyproduct that is produced as industrial waste from metal manufacture,such as TiO₂, can be applied directly at a commercial level in fields orwaste water that are rich in phosphorus, or in organic waste that can beturned to fertilizer, thus aiding agricultural enterprises to achieveoptimum crop yield and reduction in bio-available content of the soil.For the metal manufacturing industry, the result is environmentally safedisposal of the byproduct, with the added benefit of savings in the costof disposal by creating a market for the byproducts.

Accordingly, the invention is directed to a method for reducing anamount of bio-available phosphorus in an organic waste product, liquidwastewater or soil, comprising adding to the organic waste product,liquid wastewater or soil a composition or mixture comprising abyproduct from an industrial metal manufacturing process in an amountsufficient to immobilize some or all of the phosphorus present in theorganic waste product, liquid wastewater or soil. The byproduct may befrom a transition metal manufacturing process. Preferably, the byproductis from a titanium dioxide manufacturing process. According to themethod of the invention, the byproduct may be a secondary waste acidneutralization gypsum or iron oxide filter cake. The organic wasteproduct may be an animal waste. Preferably, the animal waste is poultrylitter. If the byproduct is used to remove phosphorus from liquidwastewater, the resulting precipitate, which may be suitable for landapplication, is also included. Also, the byproduct can be an aggregateof byproducts obtained through the completion of the metal manufacturingprocess.

The invention is also directed to a method for improving water qualityof surface-, subsurface-, or ground-water by reducing the amount ofsoluble phosphorus in a soil from which said water originates,comprising amending the soil surface to include a mixture comprising abyproduct from industrial metal manufacturing process. The byproduct maybe from a transition metal manufacturing process. Preferably, thebyproduct is from a titanium dioxide manufacturing process. Morepreferably, the byproduct is secondary waste acid neutralization gypsumor filter cake. In this method, the organic waste product may be animalwaste. Preferably, the animal waste is poultry litter. Also, thebyproduct may be an aggregate of byproducts obtained through thecompletion of the metal manufacturing process.

In another aspect of the invention, the invention provides a method forcontrolling the growth of an organism in a body of water to whichsurface-, subsurface- or ground-water flows, by reducing an amount ofsoluble phosphorus in a soil from which said water originates,comprising amending a soil surface to include a mixture comprising abyproduct from an industrial metal refining process. The organism thatis controlled may be a nuisance, toxic, or detrimental organism.Preferably, the organism is unicellular. More preferably, the organismis an algae, bacteria, or protist. Even more preferably, the organism tobe controlled is Pfiesteria, and in particular, Pfiesteria piscidia. Itis generally understood that the flow of phosphorus into a body of waterwill cause the growth of numerous types of organisms, especially as theinflux of phosphorus contributes to the eutrophication of the body ofwater. Therefore, controlling the phosphorus content in the surfacerunoff or leachate will control the growth of any organism that isenhanced by the presence of excess phosphorus or eutrophication of thebody of water to which the runoff or leachate flows.

In this method, the byproduct may be obtained from a transition metalmanufacturing process. Preferably, the byproduct may be obtained from atitanium dioxide manufacturing process. More preferably, the byproductis secondary waste acid neutralization gypsum or filter cake. In thismethod, the organic waste product may be animal waste. The animal wastemay be poultry litter. And in this method, the organism to be controlledmay be Pfiesteria.

The invention is also directed to a method for optimizing crop yield andphosphorus content in a soil, comprising:

-   -   i) determining the amount bio-available phosphorus present in        the soil; and    -   ii) if the amount of phosphorus determined in step i) is too        high and it is desired to control the phosphorus content, an        organic waste that has been amended with a phosphorus        immobilizing amount of a byproduct of an industrial metal        manufacturing process, is added to the soil thereby keeping        nitrogen content in the organic waste sufficient to fertilize        the crop, but controls the amount of bio-available phosphorus in        the soil.

These and other objects of the invention will be more fully understoodfrom the following description of the invention, the referenced drawingsattached hereto and the claims appended hereto.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1—A flow chart of titanium dioxide manufacturing process.

FIG. 2—Phosphorus sorption isotherm for SWAN-gypsum and Iron OxideFilter Cake

FIG. 3—Percent reduction in soluble phosphorus vs. poultry litter toSWAN or FC amendment rate. Results are from a one-week incubationmodeled after methods described in Moore, Jr., P. A., and D. M. Miller.1994. Decreasing phosphorus solubility in poultry litter with aluminum,calcium and iron amendments. J. Environ. Qual. 23: 325-330, which isincorporated herein by reference in its entirety.

FIG. 4—Percent reduction in soil test phosphorus vs. poultry litter toSWAN or FC amendment rate. Results are from a one-week incubationmodeled after methods described in Moore and Miller (1994) cited above,which is again incorporated herein by reference in its entirety.

DETAILED DESCRIPTION OF THE INVENTION

As used herein, the phrase “calcium and iron containing mixture”includes any mixture that contains calcium and iron. The calcium may bein any form, such as CaSO₄, CaCO₃, or any other combination with anyother molecule thereof, including anhydrous and hydrated forms. The ironcan be in any form, such as iron oxides or hydroxides. The calcium andiron containing mixture, when used with liquid waste, preferably doesnot significantly alter the solution pH. In a preferred embodiment, dueto the presence of both iron and calcium, the mixture effectively sorbsphosphorus in both acidic and alkaline environments, preferably in arange of about pH 4.5-8.5.

Considering the problems associated with pH adjustment, an idealphosphorus sorbing material should effectively remove phosphorus fromsolutions with neutral to slightly alkaline pH ranges typical of farmwastewater, while also maintaining the ability to sorb phosphorus inacidic environments.

According to the invention, the amount of the calcium and ironcontaining mixture that is mixed with the organic waste in order toremove the bio-available phosphorus is determined according to the needfor any particular amount of bio-available phosphorus that is desired toremain in the organic waste. That is, the amount of the calcium and ironcontaining mixture admixed with the organic waste sample is increasedwith the desire to decrease the amount of phosphorus in the organicwaste. If a greater level of phosphorus is desired to be left in theorganic waste, then fewer amounts of the calcium and iron-containingmixture is added to the organic waste.

In another embodiment of the invention, a calculation of the amount ofthe calcium and iron containing mixture required to attain a particularlevel of phosphorus in an organic waste sample is carried out, and amathematical formula can be set forth which describes and predicts theamount of phosphorus remaining in an organic waste sample aftertreatment In turn, the amount of phosphorus that is desired to remain inthe organic waste sample depends upon the phosphorus requirement of thesoil that is to be amended.

In one embodiment of the invention, “calcium and iron containingmixture” refers to a byproduct of an industrial metal oxidemanufacturing process. Preferably, the metal is a transition metal. Morepreferably, the metal belongs to Group 4. Most preferably, the metal istitanium.

Metal manufacturing processes may differ between different metals.However, any metal or metal oxide manufacturing process which produceslarge-scale, commercially applicable amounts of byproducts thatimmobilize bio-available phosphorus in soil or organic waste, that areoptionally rich in calcium and iron, and which are suitable as soiladditives alone or in combination with organic waste, as defined by theEnvironmental Protection Agency guidelines, falls within the method ofthe invention.

Although the total amount of byproducts in the aggregate obtainedthrough the completion of the manufacturing process can be used in themethod of the invention, it is also possible, and at times preferable,that selected byproducts obtained at certain points in the manufacturingprocess be used individually or together. For example, it can be readilyseen that a person of skill in the art could analyze the byproduct fromeach reaction step, and depending on the results of the analysis, andoptionally with the knowledge of the starting material and all materialsused in the manufacturing process, may favor using certain byproducts inthe method of the invention, depending on the desires and needs of theperson.

It is to be understood from the above that the amounts of iron andcalcium present in the byproduct of the industrial metal or metal oxidemanufacturing process is necessarily subject to variability depending onthe amount of chemical ingredients such as calcium and iron present inthe starting material, such as in the metal-containing ore, coke, orslag used throughout the refining or metal oxide manufacturing process.Therefore, it is understood by a person of ordinary skill in the artthat the presence of various chemical ingredients in the byproduct maynot adhere to any specific concentration range, so long as the byproductbinds bio-available phosphorus present in waste liquid, soil, or organicwaste.

It is also understood that any additive or component may be added ormixed with the byproduct to carry out the process of the invention solong as the composition or mixture possesses the property of bindingphosphorus.

As used herein, the phrase “filter cake (FC)” or “iron oxide filter cake(FC)” is a byproduct of the chlorine-based metal oxide, preferablytitanium oxide, refining process. Preferably, iron oxide filter cakerefers to the solid residue, which remains after TiO₂ has been extractedfrom the ore (or coke or slag) feedstock in the chloride manufacturingprocess. The filter cake is comprised of calcium in an amount of 0-100%by weight, preferably, 0-20%, and more preferably, 2-10%. Mostpreferably, filter cake includes calcium in an amount of about 5% byweight. The filter cake comprises iron in an amount of 0-100% by weight,preferably, 5-75%, and more preferably, 10-20%. Most preferably, filtercake includes iron in an amount of about 15% by weight.

As used herein, the phrase “secondary waste acid neutralization (SWAN)gypsum” means a byproduct resulting from neutralization of the acidicwaste stream resulting from the sulfuric acid process of extractingtitanium dioxide from ore. This process is described and set forth asthe product of ‘secondary neutralization operation’ in U.S. Pat. No.4,186,088, which is incorporated herein by reference in its entirety.SWAN-gypsum is comprised of calcium in an amount of 0-100% by weight,preferably, 10-75%, and more preferably, 15-50%. Most preferably,SWAN-gypsum includes calcium in an amount of about 23% by weight.SWAN-gypsum comprises iron in an amount of 0-100% by weight, preferably,5-75%, and more preferably, 10-20%. Most preferably, SWAN-gypsumincludes iron in an amount of about 11% by weight. Most preferably,SWAN-gypsum includes 725±51 g kg⁻¹ gypsum, 132±38 g/kg aragonite(CaCO₃), 104±22 g kg⁻¹ of goethite (FeOOH), and 22±7 g kg⁻¹ residuecomprised of quartz (SiO₂), rutile (TiO₂) and anatase (TiO₂).

As used herein, the phrase “organic waste” includes any carboncontaining byproduct of a natural or artificial process, such as decayof once living organisms or passage of organic matter through animals.Preferably, the organic waste is animal manure or biosolids fromwastewater treatment plants. More preferably, the organic waste ispoultry litter, and even more preferably, the organic waste is chickenlitter. In particular, the organic waste is solid waste. However, liquidwaste is also included.

As used herein, the term “bio-available phosphorus” means dissolvedinorganic phosphorus, and includes, but is not limited to,orthophosphate.

As used herein, “soil test phosphorus” refers to any soil test procedureused to measure soluble, total or plant available phosphorus. Commonsoil phosphorus tests include Mehlich 1 or 3.

As used herein, “amendment rate” refers to the ratio of organic waste orsoil to the amendment on a dry weight basis, such as the ratio ofpoultry litter to SWAN or FC on a dry weight basis. For example, anamendment rate of 2:1 represents two parts of organic fertilizer or soilto 1 part of poultry litter as measured by dry weight. Or, a ratio ofpoultry litter to amendment of 3:1 would be an amendment rate of “3”.

The amendment ratio for a soil or organic fertilizer source depends onseveral conditions: (1) desired phosphorus application rate, and (2)phosphorus content of fertilizer source. The first step in determiningan organic fertilizer source to amendment ratio is to obtain a soil testphosphorus analysis. Based on these and the desired phosphorusapplication rate, the amendment rate is based on either: (1) previousresearch on a similar organic fertilizer source (such as incubationexperiments) that establish amendment rates and reduction in solublephosphorus, or if no previous incubation experiments exist, (2)incubation experiments with the organic fertilizer source.

Although any calcium and iron containing mixture or composition, orpreferably an industrial byproduct from a metal refining process, can beused in the invention, SWAN-gypsum and iron oxide FC will be describedby way of illustration. It will be appreciated by those skilled in theart, that calcium and iron containing mixture or composition is notlimited by the exemplified species of SWAN-gypsum and iron oxide FCpresented herein, as these compositions are presented solely forillustrative purposes, and is not meant to limit the invention in anyway.

Results from research with calcium and iron containing mixtures,particularly with SWAN-gypsum and iron oxide filter cake, indicates thatboth materials have a high phosphorus affinity and can significantlyreduce the amount of soluble phosphorus in manure. Modeled after methodsdescribed in Moore and Miller (1994), which is cited above, and isincorporated herein by reference in its entirety with respect to theincubation protocol, one week incubation experiments with various ratiosof SWAN or FC to poultry litter demonstrated an inverse relationshipbetween amendment rate and reduction of water soluble phosphorus andsoil test phosphorus (FIGS. 3 and 4). This relationship can be used todetermine a soil and crop specific poultry litter to SWAN or FCamendment ratio suitable for application of poultry litter based on cropnitrogen requirements.

Soil test phosphorus value is the critical factor in determining whetheranimal manure can be applied according to crop nitrogen requirements.For soils that test in the “excessive phosphorus” range, nutrientmanagers are required to perform a Phosphorus Site Index (PSI)assessment (Maryland Phosphorus Site Index: Volume I, 1999 cited above,which is incorporated herein by reference in its entirety). The PSItakes into consideration factors such as soil test phosphorus, soiltype, fertilizer source and phosphorus availability, slope, bufferstrips, runoff potential and cropping methods to derive a final ratingbased on the potential for phosphorus loss to surface waters. The finalrating is based on 5 categories (high risk to low risk) on whichphosphorus application guidelines are based. A low risk rating willallow for the continued application of manure based on nitrogenrequirements, while a medium to high risk rating indicates thatphosphorus applications will either be limited to annual croprequirements or eliminated completely.

The two parameters that have the most significant impact on the finalPSI rating are soil test phosphorus and the phosphorus availabilitycoefficient of the fertilizer source (Maryland Phosphorus Site Index:Volume I, 1999). Amending soils with calcium and iron containingcompositions or mixtures, such as SWAN or FC, will reduce soil testphosphorus values. Amending manure with SWAN and FC will reduce valuesfor soil test phosphorus and the phosphorus availability coefficient.Using SWAN and FC amended manure, soils that do not currently test inthe excessive phosphorus range can maintain soil test phosphorus levelswithin acceptable limits. Alternatively, SWAN or FC is used to remediatesoils that fall into the PSI ranking for high risk of phosphorus runoff.Ultimately, soil amendments such as SWAN and FC are used as a tool byboth nutrient managers and farmers to allow for greater flexibility inthe use of manure as agricultural fertilizers.

Accordingly, in one embodiment of the invention, relationships areestablished between SWAN and FC amendment rates and reduction in theamount of soluble and soil test phosphorus for poultry litter and avariety of soils. In another embodiment of the invention, methods aredeveloped for determining rates of amendment based on soil testphosphorus, poultry litter application rate and plant nutrientrequirements.

The following examples are offered by way of illustration of the presentinvention, and not by way of limitation.

EXAMPLES Example 1 SWAN or FC Adsorption Isotherms

In soils, the primary soluble phosphorus retention mechanisms are soiladsorption and mineral precipitation. Because it is often difficult todiscern which process is occurring in soils, the term “sorption”, whichincludes adsorption and precipitation, is used. Adsorption of phosphorusoccurs via ligand exchange on surfaces of clay particles, organic peat,and calcium, ferric and aluminum oxides and hydroxides. This occurs whenoxygen or hydroxyl (OH⁻) ions are replaced by the phosphate anion (PO₄⁻). Under certain conditions, precipitation of phosphorus can occur withiron, aluminum and calcium cations. As sorption sites and cationscapable of precipitating soluble phosphorus are finite, continual,long-term application of animal waste results in the accumulation ofphosphorus in surface soils and subsequent increase in phosphorus lossvia runoff and erosion.

The nature of the phosphorus precipitate compounds formed depends on pHand relative concentrations of free Ca²⁺, Fe³⁺, and Al³⁺, althoughreduced conditions limit the concentration of Fe³⁺ (ferric iron) viareduction of Fe³⁺ to Fe²⁺ (ferrous iron). In acidic soils (below pH5.5), ferric iron and aluminum phosphorus compounds predominate with aminimum solubility at pH 3-4. Even at a pH of 6.5, much of thephosphorus is still combined with iron and aluminum. Calcium phosphateprecipitates begin to occur at a pH of 6, and at pH 6.5 the formation ofcalcium salts is a significant factor in immobilizing phosphorus. AbovepH 7.0, tricalcium phosphate (Ca₃(PO₄)₂) complexes predominate and overtime, even more insoluble calcium phosphate compounds such as apatitesare formed.

While phosphorus precipitation by free Ca²⁺, Fe³⁺, and Al³⁺ is pHdependent, fixation of phosphorus by adsorption onto clay surfaces andhydroxides and oxides of Ca, Fe, and Al occurs over a comparatively widepH range. In acidic to neutral soils, phosphorus fixation is dominatedby amorphous aluminum hydroxides and iron oxides.

Phosphorus sorption capacity of SWAN or FC is measured and comparedusing adsorption isotherms and two widely utilized equilibrium-basedadsorption models, the Langmuir and Freundlich equations. Adsorptionisotherms describe the relationship between the activity or equilibriumsolution concentration of the cation or anion in question and thequantity of the ion adsorbed on the surface at constant temperature(Sparks, Environmental Soil Chemistry. Academic Press. New York, 1995).Adsorption isotherms are constructed by equilibrating a given amount ofthe SWAN or FC with a set volume of solutions that vary in phosphorusconcentration. Initial phosphorus concentration minus equilibriumsolution concentration is assumed to be removed by the SWAN or FC. FIG.2 shows phosphorus sorption isotherm for SWAM-gypsum and iron oxidefilter cake.

Example 2 SWAN or FC in Treatment of Liquid Wastewater

Determination of appropriate SWAN or FC application rate is based onphosphorus content of the wastewater and the phosphorus removal rate ofSWAN or FC for that particular wastewater. Nutrient analysis is used todetermine the phosphorus content of wastewater. Laboratory bench topexperiments are used to establish the required concentration of theamendment per volume of wastewater. Laboratory bench top experimentswould also establish contact time necessary for phosphorus removal tooccur.

Example 3 Suitability of SWAN-gypsum and Filter Cake as Soil Amendments

The potential for trace metal contamination from SWAN-gypsum, filtercake and poultry litter was evaluated using the Resource Conservationand Recovery Act (RCRA) Toxicity Characteristic Leaching Procedure(TCLP, SW-846 Method 1311). Samples were prepared using a leaching fluidof pH 4.93±0.05, which approximates the lowest acidity expected inMaryland agricultural soils. Final pH of the solution extracts wasapproximately 7. Analysis was performed using Inductively Coupled PlasmaEmission Spectrometry (ICPES) and Cold Vapor Atomic AbsorptionSpectrometry (CVAAS) in accordance with SW-846 Methods 6010B and 7470Arespectively. Table 1 shows the results of these analysis:

TABLE 1 Results of TCLP Analysis. TCLP Limit SWAN gypsum Filter CakePoultry Litter Element (mg/L) (mg/L) (mg/L) (mg/L) Arsenic 5 <0.5 <0.5 1Barium 100 <5 <5 <5 Cadmium 1 <0.05 <0.05 <0.05 Chromium 5 <0.1 <0.1<0.2 Lead 5 <0.5 <0.5 <0.5 Mercury 0.2 <0.01 <0.01 <0.01 Selenium 1 <0.5<0.5 <1 Silver 5 <0.05 <0.05 <0.05

Results for all three materials fall well below regulatory limits.

Total metal concentrations of metals in both SWAN-gypsum and filter cakebyproducts also meet the Environmental Protection Agency (EPA)guidelines for land application (40 C.F.R. Ch. 1, Part 503, Jul. 1, 1998Edition), see Table 2.

TABLE 2 Results of Total Metals Analysis. Ceiling Concentration (Table 1of 40 CFR 503.13 SWAN gypsum Filter Cake Pollutant μg/g dry weight μg/gdry weight μg/g dry weight Arsenic 75 <0.2 4.0 Cadmium 85 <0.2 <0.2Chromium 3,000 1,210 2,200 Copper 4,300 <1.0 <1.0 Lead 840 <8.0 <8.0Mercury 57 <0.08 <0.08 Nickel 420 8.20 234 Selenium 100 <0.2 0.896 Zinc7,500 20.7 40.6

Total metal concentrations represent a worst case scenario in that theyare obtained in the laboratory using extremely rigorous digestionconditions (pH<1). It is unlikely that such conditions would beencountered in agricultural use. Furthermore, due to its high calciumcarbonate content (about 22.3%), SWAN-gypsum is expected to partiallyneutralize slightly acidic soil conditions when used in land-basedapplications. Its liming capacity was effectively demonstrated byOffiah, O. and D. S. Fanning. 1994 Liming value determination of acalcareous, gypsiferous waste for acid sulfate soil. J. Environ. Qual.23:331-337, which is incorporated herein by reference in its entirety.

Table 3 provides more comprehensive results of total metals analysis ofSWAN-gypsum and filter cake.

TABLE 3 Total metal analysis of SWAN-gypsum and Filter Cake as reportedby Millennium Inorganic, Inc. using Inductively Coupled Plasma EmissionSpectrometry (ICPES). Concentration in SWAN-gypsum Concentration in (mgkg⁻¹) on dry weight Filter Cake (mg kg⁻¹) Element basis on dry weightbasis Al 13,450 25,900 As <0.1 Not determined Ba 23 193 Cd 0.3 <0.40 Ca231,000 44,900 Cr 1,300 2,200 Cu <0.1 85 Fe 111,000 195,200 Hg 0.1 Notdetermined K 46 83.9 Mg 2,700 17,000 Mn 1,590 368,800 Na 616 3,500 Ni8.9 327 S 194,000 4,300 Se <0.1 Not determined Si 367 27,300 Ti 17,50077,000 V 3,380 8,100 Zn 31 47.3

Example 4 Incubation Experiments

The relationships between amendment rate, time and reduction of solublephosphorus, and soil test phosphorus for poultry litter and soilscommonly found in the Maryland region are investigated using a modifiedversion of incubation experiments as described by Moore and Miller(1994). SWAN-gypsum and iron oxide filter cake are mixed with thefollowing: (1) soils with elevated STP levels, (2) soils amended withpoultry litter and (3) poultry litter only. Each mix is evaluated with 5different amendment rates of SWAN and FC and three replications. Theamended soils/poultry litter is incubated in the dark at 25° C. withsoil moisture maintained at field capacity. Sub-samples are removedinitially and at weekly intervals until a plateau is observed inreduction of soluble phosphorus vs. time. Samples are analyzed for pH(1:1 soil:water), electrical conductivity, water soluble phosphorus (asdescribed in Moore and Miller, 1994) and Mehlich 3 extractablephosphorus (Mehlich, A. 1985. Mehlich 3 soil test extractant: amodification of Mehlich 2 extractant. Commun. In Soil Sci. Plant Anal.15(12): 1409-1416, which is incorporated herein by reference in itsentirety) and trace metals. Results from Mehlich 3 extractions are usedin the calculation of appropriate amendment rates for SWAN and FC.

Example 5 Greenhouse Plant Experiments

The influence of SWAN and FC on the growth of corn and soybeans areinvestigated using greenhouse pot experiments. Based on results fromincubation experiments, both SWAN amended and FC amended soils poultrylitter are investigated for their effect on plant growth as comparedwith plants grown in soils amended with poultry litter only. Methodsused in this experiment are similar to those described in Tsadilas, C.D., Theodora Matsi, N. Barbayiannis, and D. Dimoyiannis. 1995. Influenceof sewage sludge application on soil properties and on the distributionand availability of heavy metal fractions. Commun. Soil. Sci. PlantAnal. 26(15&16): 2603-2619, which is incorporated herein by reference inits entirety. Anion exchange membranes are used to measure soil solutionphosphorus concentrations in situ (Cooperband, L. R. and T. J. Logan.1994. Measuring in situ changes in labile soil phosphorus withanion-exchange membranes. Soil Sci. Soc. Am. J. 58:105-114, which isincorporated herein by reference in its entirety) to verify that soilsolution phosphorus concentrations are acceptable for plant nutrientrequirements. In addition, soil test phosphorus is measured initiallyand at monthly intervals throughout the duration of the experiment.Samples of plant material from both control and treated soils are groundand analyzed for trace metals according to methods described by (Jones,Jr., Benton, J. B. Wolf, and H. A. Mills. 1991. Plant Analysis HandbookA Practical Sampling, Preparation, Analysis, and Interpretation guide.Micro-Macro Publishing, Inc., Athens, Ga., incorporated herein byreference in its entirety).

Example 6 Rainfall Simulation Experiments

A rainfall simulator is used to investigate the effect of SWAN and FC onsoluble phosphorus in surface runoff. The literature indicates that thepotential for soluble phosphorus migration is the highest immediatelyfollowing manure application, and exponentially declines thereafter(Edwards, D. R., L. D. Norton, T. C. Daniel, J. T. Walker, D. L.Ferguson, and G. A. Dwyer. 1992. Performance of a rainfall simulator forwater quality research. Arkansas Farm Res. 41(2): 13-14, incorporatedherein by reference in its entirety). Rainfall simulation is thereforedesigned to simulate three rainfall events. Surface runoff samples arecollected and analyzed for pH, electrical conductivity, dissolvedinorganic phosphorus, total phosphorus, and dissolved organic carbon(Standard Methods for Water and Wastewater, 20^(th) Edition, 1998,incorporated herein by reference in its entirety).

Example 7 Field Plots

Field demonstration plots receiving control (unamended) and SWAN and FCamended poultry litter are planted with corn using amendment ratesderived from results of both incubation (EXAMPLE 4) and greenhouse(EXAMPLE 5) experiments. Three different rates of amendment areinvestigated for both the SWAN and FC resulting in a total of 7treatments with three replications. After harvest, the collected corn isdried and weighed so that comparisons in production between control andtreated plots are performed. Ground vegetation samples are also analyzedfor trace metals according to the methods of (Jones et al., 1911discussed in Example 5, and again incorporated herein by reference inits entirety).

Thus, a mathematical relationship is established between soil testphosphorus and SWAN-gypsum/iron oxide filter cake amendment rates. Inaddition, an appropriate formula is derived for determining applicationrates of SWAN-gypsum and iron oxide filter cake based on soil testphosphorous values and/or desired poultry litter application rates basedon crop nitrogen requirements.

All of the references cited herein are incorporated by reference intheir entirety.

1. A method for reducing an amount of bio-available phosphorus in anorganic waste product, liquid wastewater or soil, comprising the step ofadding to the organic waste product, liquid wastewater or soil acomposition or mixture comprising a byproduct from a titanium dioxidemanufacturing process in an amount sufficient to immobilize some or allof the phosphorus present in the organic waste product, liquidwastewater or soil, wherein the byproduct comprises about 2-10% byweight calcium, about 10-20% by weight iron, and about 8% by weighttitanium dioxide.
 2. The method of claim 1, wherein the byproductcomprises about 5% by weight calcium and about 15% by weight iron. 3.The method of claim 1, wherein said organic waste product is animalwaste.
 4. The method of claim 3, wherein said animal waste is poultrylitter.
 5. The method of claim 1, wherein said byproduct is secondarywaste acid neutralization gypsum or filter cake.
 6. A method forreducing an amount of bio-available phosphorus in an organic wasteproduct, liquid wastewater or soil, comprising the step of adding to theorganic waste product, liquid wastewater or soil a composition ormixture comprising a byproduct from a titanium dioxide manufacturingprocess in an amount sufficient to immobilize some or all of thephosphorus present in the organic waste product, liquid wastewater orsoil, wherein the byproduct comprises about 15-50% by weight calcium,about 10-20% by weight iron, and about 2% by weight titanium dioxide. 7.The method of claim 6, wherein the byproduct comprises about 23% byweight calcium and about 11% by weight iron.
 8. The method of claim 6,wherein said organic waste product is animal waste.
 9. The method ofclaim 8, wherein said animal waste is poultry litter.
 10. The method ofclaim 6, wherein said byproduct is secondary waste acid neutralizationgypsum or filter cake.
 11. A method for controlling the growth of anorganism in a body of water to which surface-, subsurface-, orground-water flows, by reducing an amount of soluble phosphorus in asoil from which said water originates, comprising the step of amendingthe soil to include a mixture comprising a byproduct in an amountsufficient to immobilize some or all of the phosphorus present in thesoil; said by-product comprising calcium, iron and titanium dioxide. 12.The method of claim 11, wherein said byproduct is obtained bymanufacturing titanium dioxide by chemically processing a titaniumdioxide starting material and obtaining said product containing calcium,iron and titanium dioxide.
 13. The method of claim 12, wherein thestarting material is ore, coke, or slag.
 14. The method of claim 12,wherein said chemical process is chlorine based.
 15. The method of claim12, wherein said byproduct comprises about 2-10% by weight calcium,about 10-20% by weight iron, and about 8% by weight titanium dioxide.16. The method of claim 15, wherein the byproduct comprises about 5% byweight calcium and about 15% by weight iron.
 17. The method of claim 16,wherein said chemical process is sulfuric acid based.
 18. The method ofclaim 17, wherein the byproduct comprises about 15-50% by weightcalcium, about 10-20% by weight iron, and about 2% by weight titaniumdioxide.
 19. The method of claim 18, wherein the byproduct comprisesabout 23% by weight calcium and about 11% by weight iron.
 20. The methodof claim 11, wherein said organism is algae.
 21. The method of claim 11,wherein said organism is bacteria.
 22. The method of claim 21, whereinsaid bacteria is Pfiesteria.
 23. The method of claim 22, wherein saidbacteria is Pfiesteria piscidia.
 24. A method of controllingeutrophication in a body of water, which comprises the step of reducingan amount of soluble phosphorus flowing into said body of water fromsurface, subsurface or ground-water flows, by immobilizing some or allof the phosphorus present in a soil through which said surface,subsurface or ground-water flows pass; said immobilizing being effectedby a byproduct comprising calcium, iron and titanium dioxide.
 25. Amethod for reducing an amount of bio-available phosphorus in soilcontaminated therewith, comprising the step of adding a by-productcomprising calcium, iron and titanium dioxide to the soil in an amountsufficient to immobilize some or all of said bio-available phosphorus inthe soil.
 26. The method of claim 25, wherein the bio-availablephosphorus in soil contaminated therewith is from animal waste.
 27. Themethod of claim 26, wherein the animal waste is poultry litter.
 28. Themethod of claim 27, wherein the poultry litter is chicken litter. 29.The method of claim 25, wherein said by-product is secondary waste acidneutralization gypsum or filter cake.
 30. The method of claim 25,wherein said by-product is produced by a process which comprises thesteps of chemically processing a titanium dioxide-containing startingmaterial.
 31. The method of claim 25, wherein said by-product comprisesabout 2-10% by weight calcium, about 10-20% by weight iron, and about 8%by weight titanium dioxide.
 32. The method of claim 31, wherein saidcalcium is present in the amount of about 5% by weight, and said iron ispresent in the amount of about 15% by weight.
 33. The method of claim25, wherein said by-product comprises about 15-50% by weight calcium,about 10-20% by weight iron and about 2% by weight titanium dioxide. 34.The method of claim 33, wherein said calcium is present in the amount ofabout 23% by weight, and said iron is present in the amount of about 11%by weight.
 35. The method of claim 5, wherein said filter cake is ironoxide filter cake.
 36. The method of claim 29, wherein said filter cakeis iron oxide filter cake.
 37. The method of claim 25, wherein saidamount sufficient to immobilize some or all of said bio-availablephosphorus in the soil is determined by a process comprising the stepsof: a) reassuring soil phosphorus content by soil testing, and b)referring to an incubation experiment to determine an amendment amount.38. The method of claim 24, wherein said same or all of the phosphorousin the soil is from animal waste.
 39. The method of claim 38, whereinsaid animal waste is poultry litter.
 40. The method of claim 39, whereinsaid poultry litter is chicken litter.